Dealing with Cold Spots in Custom Glassware
If you’ve ever worked with custom glass shapes or bottle cutters, you know the headache. You pull a piece out of the kiln, thinking it’s fine, and then—snap. It happens because complex shapes, like a narrow neck or a wide, flared base, are a nightmare for heat. In a standard kiln, you get these “cold spots.” The glass just doesn’t soak up the heat evenly, leaving internal stress that eventually kills the piece. It’s frustrating.
Why IR Lamps Actually Work
Here is the thing: convection heat is lazy. It struggles to get into those tight gaps. That’s why we use shortwave infrared lamps. Instead of relying on hot air to drift around, IR radiation travels in straight lines and hits the glass surface directly. By angling these lamps from a few different directions, you can basically “attack” the glass from every side. No more dead zones.
Getting the Hardware Right
When you’re wiring this up, it all comes down to heat density. If you’re dealing with thick-walled glass, you need a high-wattage quartz tube. It gives you that concentrated punch of energy to get the temperature up fast. Just make sure your lamp length matches the widest part of your vessel, or you’ll end up with gaps in your coverage. We stick with quartz envelopes because they don’t freak out when the temperature swings rapidly. Also, a quick tip: check your control panel’s current draw. If you’re running high voltage, you don’t want to be the person tripping the breakers the second you ramp up the heat.
The Balancing Act
You can’t just toss these lamps in and hope for the best. It’s all about the distance. If the lamp is too close? You’ll get hot spots that can actually warp or deform the glass. Too far? You lose all that energy density and you’re back to square one. You’ll have to play around with the distance based on how thick your glass is. Once you find that sweet spot, lock everything down with a solid mounting bracket. You don’t want your lamps shifting around while the kiln is screaming.